An event, `m_signal`, is created and signalled when either `m_running` or
`m_connected` is changed by another thread, so that the pipe thread knows
to interrupt the read.
The pipe is now opened as async to allow interruption, and the I/O
operations now use overlapped I/O.
Other changes include:
* Changing `m_pipe` to `HandleT<HANDLETraits>` since `CreateFile` returns
`INVALID_HANDLE_VALUE` instead of `NULL` on error.
* Remove the call to `WaitNamedPipeA` because it's useless and returns
immediately without waiting if the pipe doesn't exist.
As the IDD itself runs in a WUMDF sandbox, it doesn't have enough
access to perform interactive operations such as moving the cursor.
This helper service communicates with the IDD over a named pipe,
so that we can perform these things, as well as in the future provide
a configuration GUI.
